At the height of his power , Zhou Yongkang controlled police forces , spy agencies , court systems and prosecution offices across China -- and the domestic security czar was n't shy in deploying his vast assets to crush dissent and unrest in the name of `` preserving social stability . ''

During his reign before retiring in 2012 , as worsening income inequality and official corruption fueled mass discontent nationwide , Zhou oversaw the domestic security budget swell to surpass that of the two million-strong Chinese military -- the world 's largest .

As a member of the ruling Communist Party 's Politburo Standing Committee -- China 's top decision-making body -- Zhou was one of nine men who effectively ruled the country of more than 1.3 billion people .

Away from the spotlight , though , Zhou and his family members were reportedly taking advantage of his leadership position to accumulate enormous wealth . The allegedly blatant exchange between money and power , as revealed by China 's state media , would eventually prompt Zhou 's shocking downfall last summer .

After months of intense political rumors , the Communist Party 's disciplinary arm in late July announced an official investigation into Zhou for `` serious disciplinary violations . '' On Friday , state prosecutors alleged the investigation found that Zhou , 71 , had taken advantage of his positions to garner profits for others , and had `` accepted huge bribes personally and through his family . ''

Zhou was also expelled from the Communist Party , according to state news agency Xinhua , citing a decision made Friday at a meeting of the party central committee 's political bureau .

Anti-corruption campaign

Many have viewed his fall from grace as a watershed moment in the secretive world of Chinese politics now ruled by President Xi Jinping , who has been spearheading a massive anti-corruption campaign ostensibly targeting `` tigers and flies '' -- high-ranking and low-level officials -- alike .

`` The important thing here is that Xi has proven he 's powerful enough to break this taboo of never incriminating former Politburo Standing Committee members , '' said longtime political analyst Willy Lam with Chinese University of Hong Kong .

Unlike Xi , who is `` Communist royalty '' thanks to his father 's status as one of Chairman Mao 's comrades in arms during the revolution , Zhou was born to a poor family in eastern China .

His father was an illiterate farmer but borrowed money to send him to school . Smart and hardworking , Zhou did n't disappoint and went on to become one of the few local students admitted into an elite university in Beijing .

That school , now called China University of Petroleum , was the cradle for titans in the state oil industry . After graduating with a degree in oil exploration , Zhou was assigned to an oil field in the country 's northeast and rose through the official ranks from the late 1960s through the mid-1980s .

Described by many as a capable and humbling young party cadre , Zhou was remembered more for his political savviness than technical knowledge . His political skill shone when he was transferred to the oil ministry in Beijing , which later became a giant state-owned oil company and one of Zhou 's power bases .

Decisive leader

Overcoming factional wars in the ministry , Zhou was said to be a decisive leader who focused on expanding domestic oil exploration as well as overseas projects , a two-pronged strategy that would continue to this day . Fast growth of business abroad made supervision from Beijing harder , sowing the seeds for corruption .

In 2001 , after a stint as minister of land resources , Zhou was named the Communist Party chief of Sichuan in southwest China , one of the country 's most populous provinces . State media there portrayed Zhou as an eloquent leader with a clear vision , and credited him for luring high-tech companies including Intel to the southwestern province , as well as modernizing the agriculture and tourism sectors .

Zhou also developed strong local ties and planted officials loyal to him -- including secretaries he brought from Beijing -- in key postings throughout the province .

Zhou 's big break came in 2002 when he returned to Beijing and was put in charge of the ministry of public security , which runs the country 's police forces .

Five years later , he rose to the apex of power by taking a seat in the nine-member Politburo Standing Committee -- with an expanded portfolio that covered all domestic security affairs .

His reign coincided with a time of mounting social and ethnic unrest as well as such major events as the Beijing Olympics in 2008 , the 60th anniversary of the People 's Republic in 2009 and the World Expo in Shanghai in 2010 .

Ruthless hardliner

As the leadership prioritized security and stability above all else , Zhou greatly expanded police power at the expense of already-limited judicial independence , cementing his reputation as a ruthless hardliner among political dissidents and activists .

It was also during this period that Zhou became a patron of Bo Xilai , a fast-rising political star who was waging his own controversial war against organized crime in the southwestern metropolis of Chongqing .

Bo 's spectacular downfall in 2012 -- complete with tales of murder , bribery and betrayal -- attracted global attention . State media cited his subsequent conviction on corruption charges as a prime example of Xi 's resolve to clean up the party .

Bo supporters , however , have long called him a political victim as the former high-flying politician was once considered Xi 's main challenger for the top spot of Chinese leadership . Political activists and observers now note the similarity between the Bo and Zhou cases .

`` Zhou challenged Xi 's authority and threatened his rule -- that 's why he 's now being held responsible along with his gangs , '' offered Hu Jia , one of China 's leading political dissidents , who was thrown into prison for more than three years on `` subversion '' charges when Zhou first took over nationwide law enforcement .

`` The bottom line is : All officials are corrupt , '' he added . `` Xi ca n't find a better excuse to rid of his political opponents than fighting corruption -- something that helps him win the masses ' hearts and minds .

`` The people being investigated for corruption are on the losing side of factional struggles , '' echoed Lam , the Hong Kong analyst . `` People who are close to Xi are less liable to becoming incriminated . ''

Zhou 's family , aides probed

Those close to Zhou have fallen with him . State media have reported official investigations -- and formal arrests in some cases -- into dozens of Zhou 's family members and former aides . The biggest impact was felt in the domestic security apparatus , state oil industry and Sichuan province -- three places Zhou once ruled .

Details have also emerged in Chinese media about possible skeletons in Zhou 's closet , including the suspicious circumstances surrounding the death of his first wife . Most stories , though , have focused on the vast wealth amassed by Zhou 's older son as well as his two brothers and their families . The Zhous reportedly benefited immensely from China 's booming energy and real estate sectors thanks to Zhou 's deep ties to the two related ministries .

Zhou 's older son , who is 42 , is said to own multiple luxury properties worth millions of dollars . Before even turning 30 , the younger Zhou 's first foray into business met with fast growth and quick success after winning a contract to upgrade IT systems for 8,000 gas stations across China . His companies also reportedly reaped huge financial gain from buying and selling oil fields and hydropower stations .

State media reports also indicated that one of Zhou 's younger brothers , a onetime farmer , used Zhou 's influence to launch a `` crisis management '' business and profited from helping people get out of jail , enter police academy and sell steel pipes to state-owned oil fields .

Other published articles have painted an intricate web of officials , cronies and tycoons -- some with alleged mafia connections -- orbiting around the domestic security czar before the crumbling of his power structure .

`` I think , unlike Bo Xilai , Zhou Yongkang will cooperate with investigators because his family is involved , '' said analyst Lam , predicting a suspended death sentence for both Zhou and his older son . `` His only incentive now is to protect his son -- he will toe the line to protect his son . ''

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Zhou arrested as part of corruption probe , expelled from Communist Party

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Zhou Yongkang was a member of the ruling Communist Party 's Politburo Standing Committee

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He 's the highest-ranking official to get caught up in President Xi Jinping 's anti-corruption campaign

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Zhou was also a patron of Bo Xilai , a former a fast-rising political star who was jailed for graft